TWI509476B - Control circuit and control method for touch panel, touch panel input device and electronic apparatus - Google Patents

Description

Touch panel control circuit, control method, and touch panel input device and electronic device using same

The present invention relates to a resistive film type touch panel, and more particularly to a technique for detecting simultaneous contact with a plurality of points (multi-touch).

In electronic devices such as computers or mobile phone terminals and PDAs (Personal Digital Assistants) in recent years, products having input devices for operating electronic devices by finger contact have become mainstream. As such an input device, a resistive film type touch panel (touch sensor) or the like is known (Patent Document 1).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-48233

In recent years, it is desirable to have a multi-touch touch panel. However, the current multi-touch panel is implemented only by an electrostatic sensor type touch panel, and has not been implemented by a resistive touch panel. The reason is that in the resistive film type touch panel, when the position (coordinate) touched by the user is determined according to the voltage output from the panel, it is impossible to distinguish the panel when the touch is 2 points (multi-touch). The output voltage is the output voltage of the panel when the touch is 1 point (single touch).

Patent Document 1 discloses a touch panel input device capable of detecting multi-touch, but it treats multi-touch as an erroneous input, and does not actively treat multi-touch as an effective input. Therefore, there is no disclosure of a technique for specifying coordinates of a plurality of points accompanying multi-touch.

The present invention has been made in view of the above problems, and one of the objects exemplified in one aspect thereof is to provide a control technology for a touch panel capable of coping with multi-touch.

1. One aspect of the present invention relates to a method of controlling a touch panel. The touch panel to be controlled includes: first, second, and third terminals; and a first resistive film that is connected to the first terminal and that is connected to the second terminal at a side opposite to the side; and the second resistive film It is disposed in a gap from the first resistive film and is connected to the third terminal. The control method includes the steps of applying a specific first and second bias voltages to the first and second terminals, detecting a panel voltage generated in the third terminal, and detecting that a first terminal and a first resistor are included in the first terminal. The panel current of the path of the film and the second terminal; and the coordinates of the point contacted by the user based on the panel voltage and the panel current.

When the user touches a plurality of points of the touch panel, the combined resistance value of the path from the first terminal to the second terminal decreases, and the panel current corresponding thereto changes. According to this aspect, the multi-touch can be preferably detected by monitoring the panel current, and the coordinates of the plurality of points can be determined.

When the value of the panel current is greater than a specific value, it can be determined that the user touches a plurality of points.

When the user touches 2 points, the coordinate interval of 2 points can be determined according to the value of the panel current. The larger the panel current, the greater the coordinate interval between the two points.

When the user touches two points, since the first resistive film and the second resistive film are connected in parallel between the two points, the combined resistance of the path from the first terminal to the second terminal is lowered, and thus the panel current is increased. The larger the distance between the two points is, the longer the distance between the first resistive film and the second resistive film is connected in parallel, so that the combined resistance is smaller, and the panel current is larger. Therefore, the coordinate interval of 2 points can be determined according to the panel current.

The coordinate interval of 2 points can also be determined according to the difference between the panel current measured when the user is not in contact with the panel and the panel current measured at the time of contact.

The determining step may include the steps of: determining a center coordinate of 2 points according to the panel voltage; and adding a value corresponding to the coordinate interval of the 2 points to determine the coordinate of one of the 2 points, and subtracting from the central coordinate The value corresponding to the coordinate interval of 2 points is used to determine the coordinates of the other of the 2 points.

Another aspect of the invention is a control circuit. The control circuit includes a voltage generating unit that applies a specific first and second bias voltages to the first and second terminals of the touch panel, and a voltage detecting unit that detects a panel voltage generated in the third terminal; a current detecting unit that detects a panel current flowing through a path including the first terminal, the first resistive film, and the second terminal; and a coordinate determining unit that determines a point touched by the user based on a panel voltage and a panel current value coordinate.

The coordinate determination unit may determine that the user touches a plurality of points when the value of the panel current is greater than a specific value.

When the user touches 2 points, the coordinate interval of 2 points can also be determined according to the value of the panel current.

The coordinate interval of 2 points can also be determined according to the difference between the panel current measured when the user is not in contact with the panel and the panel current measured at the time of contact.

The coordinate determining unit may determine the center coordinate of the two points according to the panel voltage, and add a value corresponding to the coordinate of the two points to determine the coordinate of one of the two points, and subtract from the central coordinate. The coordinates of the coordinates of 2 points correspond to each other, thereby determining the coordinates of the other of the 2 points.

The current detecting unit may further include: a detecting resistor provided on an extension line including a path of the first terminal, the first resistive film, and the second terminal; and a bypass switch provided in parallel with the detecting resistor. The bypass switch may be turned on when the panel voltage is detected by the voltage detecting unit, and the bypass switch is turned off when the panel current is detected by the current detecting unit, and the value corresponding to the voltage drop of the detecting resistor is set. It is output as a value indicating the panel current.

According to this aspect, the panel current can be measured and the influence of the sense resistor on the panel voltage can be eliminated.

Still another aspect of the present invention relates to a touch panel input device. The touch panel input device includes: a touch panel; and a control circuit of any of the above aspects, wherein the control panel controls the touch panel; and the touch panel includes: first, second, and third terminals; and a first resistive film, One side is connected to the first terminal, and the second terminal is connected to the side opposite to the side, and the second resistive film is disposed apart from the first resistive film and is connected to the third terminal.

Yet another aspect of the invention is an electronic machine. The electronic device includes the above touch panel input device.

2. One aspect of the present invention relates to a control circuit for a touch panel. The touch panel includes: first, second, and third terminals; and a first resistive film that is connected to the first terminal and that is connected to the second terminal at a side opposite to the side; and the second resistive film The first resistive film is disposed with a gap therebetween and is connected to the third terminal. The control circuit includes a voltage generating unit that applies a specific first and second bias voltages to the first and second terminals of the touch panel, and a voltage detecting unit that detects a panel voltage generated in the third terminal; The detecting unit detects a panel current flowing through a path including the first terminal, the first resistive film, and the second terminal, and a coordinate determining unit that determines a coordinate touched by the user based on the panel voltage and the panel current. The voltage generating unit includes an output transistor that is provided on an extension line including a first terminal, a first resistor film, and a second terminal on a first terminal side, and a regulator that applies a first bias to the first terminal. Voltage. The current detecting unit includes: a detecting transistor connected to the output transistor in a current mirror form; and a detecting resistor disposed on the path of the detecting transistor; and a value corresponding to a voltage drop of the detecting resistor as a panel current The value is output.

When the user touches a plurality of points of the touch panel, the combined resistance of the path from the first terminal to the second terminal decreases, and the panel current corresponding thereto changes. According to this aspect, the multi-touch can be preferably detected by monitoring the panel current, and the coordinates of the plurality of points can be determined. Moreover, since the detecting resistor for detecting the panel current is not provided in a path including the first terminal, the first resistive film, and the second terminal, and is disposed on another path different therefrom, the panel voltage is not affected. The panel current is detected in case.

Another aspect of the present invention is also directed to a control circuit for a touch panel. The touch panel includes: first, second, third, and fourth terminals; and a first resistive film connected to the first terminal at one side, connected to the second terminal at a side opposite to the side; and a second resistive film, This is disposed so as to be spaced apart from the first resistive film, and is connected to the third terminal, and is connected to the fourth terminal at the side opposite to the side. The control circuit includes a voltage generating unit that applies a specific first and second bias voltages to the first and second terminals in the first state, and causes the third and fourth terminals to be in a high impedance state, and is in the second state. In the state, the first and second bias voltages are applied to the third and fourth terminals, respectively, and the first and second terminals are in a high impedance state, and the voltage detecting unit detects the third in the first state. The panel voltage generated in one of the fourth terminals detects the panel voltage generated in one of the first and second terminals in the second state, and the current detecting unit detects that the first terminal is included in the first state. a panel current of a path between the first resistive film and the second terminal detects a panel current flowing through a path including the third terminal, the second resistive film, and the fourth terminal in the second state; and a coordinate determining unit according to the coordinate determining unit The values of the panel voltage and the panel current determine the coordinates that the user is in contact with. The voltage generating unit includes a regulator having an output transistor and generating a first bias voltage, and a selector that receives the first bias voltage at the input terminal and has a first terminal connected to the first output terminal. The third terminal is connected to the output terminal, and the first output terminal side is turned on in the first state, and the second output terminal side is turned on in the second state. The current detecting unit includes: a detecting transistor connected to the output transistor in a current mirror form; and a detecting resistor disposed on the path of the detecting transistor; and a value corresponding to a voltage drop of the detecting resistor as a panel current The value is output.

According to this aspect, the coordinates of the multi-touch and the plurality of points can be determined in both the X direction and the Y direction. Moreover, since the detecting resistor for detecting the panel current is not directly connected to the touch panel, the panel current can be detected without affecting the panel voltage.

Yet another aspect of the invention is also directed to a control circuit. In this aspect, the voltage detecting unit individually detects the panel voltages generated in the third and fourth terminals in the first state, and individually generates the first and second terminals in the second state. Panel voltage.

The current detecting unit is configured to switch the mirror ratio of the output transistor to the detecting transistor in the first state and the second state.

Further, the current detecting unit may be configured to switch the resistance value of the detecting resistor in the first state and the second state.

When the longitudinal length and the lateral length (ie, the aspect ratio) of the touch panel are largely different, the composite resistance in the vertical direction is different from the combined resistance in the lateral direction, and the range of the panel current in the X direction and the Y direction is different. In this case, by switching the mirror ratio or the value of the sense resistor, the range of the voltage drop of the sense resistor can be made uniform.

The coordinate determination unit may determine that the user touches a plurality of points when the value of the panel current is greater than a specific value.

When the user touches 2 o'clock, the coordinate interval of 2 o'clock can also be determined according to the value of the panel current. The larger the panel current, the greater the coordinate interval between the two points.

When the user touches the two points, the first resistive film and the second resistive film are connected in parallel between the two points, so that the combined resistance of the path from the first terminal to the second terminal is reduced, whereby the panel current is increased. The larger the distance between the two points is, the longer the distance between the first resistive film and the second resistive film is connected in parallel, so that the combined resistance is smaller, and the panel current is larger. Therefore, the coordinate interval of 2 points can be determined according to the panel current.

The coordinate interval of 2 points can also be determined according to the difference between the panel current measured when the user is not in contact with the panel and the panel current measured at the time of contact.

The coordinate determining unit may determine the center coordinate of two points according to the panel voltage, and add a value corresponding to the coordinate interval of the two points to determine the coordinate of one of the two points, and subtract from the central coordinate. The coordinates of the coordinates of 2 points correspond to each other, thereby determining the coordinates of the other of the 2 points.

Yet another aspect of the present invention is a touch panel input device. The device comprises a touch panel and any one of the above control circuits for controlling the touch panel.

Yet another aspect of the invention is an electronic machine. The electronic device includes the above touch panel input device.

Further, any combination of the above constituent elements and the expression of the present invention between methods, apparatuses, and the like is also effective as an aspect of the present invention.

According to one aspect of the invention, multi-touch input can be detected.

Hereinafter, the present invention will be described based on preferred embodiments and with reference to the drawings. The same or equivalent components, members, and processes are designated by the same reference numerals, and the description thereof will be omitted as appropriate. Further, the embodiments are merely illustrative and not limiting, and all features or combinations described in the embodiments are not necessarily essential parts of the invention.

In the present specification, the "state in which the member A and the member B are connected" includes, in addition to the case where the member A and the member B are directly connected to each other physically, the member A and the member B are also connected to other members that do not affect the electrical connection state. Indirectly connected.

Similarly, the "state in which the member C is disposed between the member A and the member B" includes, in addition to the case where the member A and the member C are directly connected to each other, and the member B is not directly affected by the electrical connection state. The case where other components are indirectly connected.

(First embodiment)

Fig. 1 is a block diagram showing the configuration of an electronic device 1 including a touch panel input device (abbreviated as an input device) 2 according to the first embodiment. The input device 2 is disposed, for example, on the surface layer of an LCD (Liquid Crystal Display) 8, and functions as a touch panel. The input device 2 determines the X coordinate and the Y coordinate of the point at which the user touches with a finger or a stylus pen (hereinafter referred to as finger 6).

The input device 2 includes a touch panel 4 and a control circuit 100. The touch panel 4 is a 4-wire (4-terminal) resistive film type touch panel. Since the configuration of the touch panel 4 is a common configuration, it will be briefly described herein.

The touch panel 4 includes a first terminal P1x to a fourth terminal P2y, a first resistive film RF1, and a second resistive film RF2.

The first resistive film RF1 and the second resistive film RF2 are arranged to overlap each other at intervals in the Z-axis direction perpendicular to the X-axis and the Y-axis. One side E1 of the first resistive film RF1 perpendicular to the X-axis is connected to the first terminal P1x. The side E2 opposite to the side E1 is connected to the second terminal P2x. The third terminal P1y is connected to one side E3 parallel to the X axis of the second resistive film RF2, and the fourth terminal P2y is connected to one side E4 opposite to the side E3 of the second resistive film RF2.

The above is the configuration of the touch panel 4.

The control circuit 100 determines the position of the point where the user touches by switching between the first state Φx detecting the coordinate in the X direction and the second state Φy detecting the coordinate in the Y direction.

The control circuit 100 includes a first terminal Pc1x to a fourth terminal Pc2y, a voltage generating unit 10, a voltage detecting unit 20, a current detecting unit 30, and a computing unit 40.

The first terminal Pc1x to the fourth terminal Pc2y are respectively connected to the corresponding first terminal P1x to fourth terminal P2y on the touch panel 4 side.

First, the configuration for detecting the coordinate (X coordinate) in the X direction will be described.

In the first state Φx, the voltage generating unit 10 applies a specific first bias voltage Vb1 and a second bias voltage Vb2 to the first terminal P1x and the second terminal P2x, respectively. Here, Vb1>Vb2 is made. The second bias voltage Vb2 is preferably a ground voltage (0 V). In the first state, the voltage generating unit 10 sets the third terminal P1y and the fourth terminal P2y to a high impedance state.

The voltage detecting unit 20 detects the panel voltage VPx generated in the third terminal P1y in the first state Φ x . The voltage detecting unit 20 includes an A/D converter 24 that converts the detected panel voltage VPx into a signal VPx'.

The current detecting unit 30 detects the panel current IPx flowing through a path including the first terminal P1x, the first resistive film RF1, and the second terminal P2x in the first state Φx. The current detecting unit 30 includes an I/V (current/voltage) converting unit 32 that converts the panel current IPx into a voltage signal, and an A/D (analog/digital) that converts the voltage signal into a digital signal VPx'. Analog/digital converter 34.

The calculation unit (coordinate determination unit) 40 determines the X coordinate of the point PU that the user touches based on the values of the panel voltage VPx' and the panel current IPx'.

Next, the configuration for detecting the coordinate (Y coordinate) in the Y direction will be described.

In the second state Φy, the voltage generating unit 10 applies a specific first bias voltage Vb1 and a second bias voltage Vb2 to the third terminal P1y and the fourth terminal P2y, respectively. Further, in the second state, the voltage generating unit 10 sets the first terminal P1x and the second terminal P2x to a high impedance state. The first bias voltage Vb1 in each of the first state and the second state may be the same value or a different value. Hereinafter, a case where the first bias voltage Vb1 has the same value will be described. The second bias voltage Vb2 is also the same.

The voltage detecting unit 20 detects the panel voltage VPy generated in the first terminal P1x in the second state Φ y . The A/D converter 24 converts the detected panel voltage VPy into a digital signal VPy'. The voltage detecting unit 20 is provided with a selector 22 having two input terminals, and the first input terminal (0) is connected to the third terminal P1y, and the second input terminal (1) is connected to the first terminal P1x. The selector 22 turns on the first input terminal (0) side in the first state Φx, and turns on the second input terminal (1) side in the second state Φ x.

Further, in the first state Φx, the voltage detecting unit 20 may be generated in the fourth terminal P2y instead of the voltage generated in the third terminal P1y or in addition to the voltage generated in the third terminal P1y. The voltage is used as the panel voltage VPx. Similarly, in the second state Φy, the voltage detecting unit 20 may be generated in the second terminal P2x instead of the voltage generated in the first terminal P1x or in addition to the voltage generated in the first terminal P1x. The voltage is used as the panel voltage VPy.

The current detecting unit 30 detects a panel current IPy flowing through a path including the third terminal P1y, the second resistive film RF2, and the fourth terminal P2y in the second state Φy. The I/V conversion unit 32 converts the panel current IPy into a voltage signal, and the A/D converter 34 converts the panel current IPy into a digital value IPy'.

The calculation unit (coordinate determination unit) 40 determines the Y coordinate of the point PU that the user touches based on the values of the panel voltage VPy' and the panel current IPy'.

In other words, the third terminal P1y functions as a terminal for detecting the panel voltage VPx in the first state Φx and for applying the bias voltage Vb2 to the second resistive film RF2 in the second state Φy. Similarly, the first terminal P1x functions as a terminal for detecting the panel voltage VPy in the second state Φy and a bias voltage Vb1 for the first resistive film RF1 in the first state Φx. Further, the fourth terminal P2y may be used as a terminal for detecting the panel voltage VPx instead of the third terminal P1y, and the second terminal P1y may be used as a terminal for detecting the panel voltage VPy instead of the first terminal P1x.

The above is the overall configuration of the control circuit 100. Next, the principle of detecting the coordinates by the control circuit 100 will be described. Here, the principle of detecting the X coordinate in the first state Φx will be described, but the Y coordinate is also the same.

2(a) and 2(b) are equivalent circuit diagrams showing a single touch state and a multi-touch state, respectively. Furthermore, the respective resistors shown in the equivalent circuit are actually generated as distribution constants, and are shown as individual resistor elements for simplicity of explanation.

(single touch state)

Refer to Figure 2(a). When the user touches the PU at one point, the first resistive film RF1 is divided into a resistor R11 between the first terminal P1x and the point PU, and a resistor R12 between the point PU and the second terminal P2x. When the contact is made to the point PU, the contact resistance between the first resistive film RF1 and the second resistive film RF2 is Rc. The resistance from the point PU of the second resistive film RF2 to the path of the third terminal P1y is R2.

The potential of the point PU is obtained by dividing the bias voltages Vb1 and Vb2 by the resistors R11 and R12, and thus indicates the X coordinate of the point PU. The potential of the PU is approximately equal to the voltage of the third terminal P1y. That is, the panel voltage VPx generated in the third terminal P1y represents the X coordinate of the point PU.

The algorithm for deriving the X coordinate from the panel voltage VPx can employ a well-known technique, and is not particularly limited in the present invention.

Since the impedance on the side of the third terminal P1y observation control circuit 100 is extremely high ^{, the} panel current IPx flows through the path of the first terminal P1x, the resistors R11 and R12, and the second terminal P2x. That is, the impedance Zs between the first terminal P1x and the second terminal P2x can be given by:

Zs=R11+R12;

It is considered that Zs is a constant value irrespective of the position of the contact point PU, and is also a value that is substantially the same as the impedance Zo when the user is not in contact:

Zs≒Zo.

Hereinafter, the impedance of the non-contact state and the single-touch state is not particularly distinguished and is referred to as a reference impedance Zo.

In the single-touch state or the non-contact state, the panel current IPx flowing from the first terminal P1x to the second terminal P2x can be given by:

IPxo=(Vb1-Vb2)/Zo.

This panel current IPxo is referred to as a reference panel current.

(multi-touch state)

Refer to Figure 2(b). When the user touches the two points PU1 and PU2, the first resistive film RF1 is divided into the resistor R11 between the first terminal P1x and the point PU1, the resistor R12 between the point PU1 and the point PU2, and the point PU2 and the second terminal. Resistance R13 between P2x. When contacting the points PU1 and PU2, the contact resistances of the first resistive film RF1 and the second resistive film RF2 are Rc1 and Rc2, respectively.

In the second resistive film RF2, the resistance between the points PU1 and PU2 is R21, the resistance of the path from the point PU1 to the third terminal P1y is R22, and the resistance of the path from the point PU2 to the third terminal P1y is R23.

The panel current IPx in the multi-touch state depends on the combined impedance Zm between the first terminal P1x and the second terminal P2x. The resultant impedance Zm has the following relationship with the impedance Zo of the non-contact state or the single-touch state:

Zm<Zo.

Therefore, the following relationship exists between the panel current IPxm in the multi-touch state and the reference panel current IPxo:

IPxm>IPxo.

That is, by monitoring the panel current IPx and comparing it with the reference panel current IPxo, the multi-touch state and the single-touch state (non-contact state) can be distinguished.

The potentials of the points PU1 and 2 are obtained by dividing the bias voltages Vb1 and Vb2 by the resistors R11, R12, and R13 and other resistance components, and are associated with the respective X coordinates of the points PU1 and PU2. Further, the panel voltage VPx3 generated in the third terminal P1y is also associated with the two points PU1 and PU2. Therefore, if the multi-touch state is known, the coordinates of the points PU1 and PU2 can be estimated from the panel voltage VPx.

Further, according to the panel voltage VPx3, one X coordinate X3 determined by the same algorithm as the single touch state indicates the coordinates of any point between the points PU1 and PU2 that the user touches. That is, when the true X coordinates X1 and X2 of the points PU1 and PU2 are written, the following relationship exists:

X1 < X3 < X2.

That is, if the coordinates X3 derived from the panel voltage VPx3 are used, the coordinates of the points PU1 and PU2 can be estimated. As for the inference algorithm, it will be explained below.

As described above, according to the control circuit 100 of the first embodiment, the panel current IPx is monitored in addition to the monitor panel voltage VPx, and the combination is processed to determine not only the single touch state but also the multi-touch. The coordinates of the user contact point in the controlled state.

Next, a specific configuration example and processing of the arithmetic unit 40 will be described.

The calculation unit 40 includes a multi-touch determination unit 42, a distance calculation unit 44, a table 46, and a coordinate generation unit 48.

3 is a flow chart of the processing in the control circuit 100 of FIG. 1. The flow of Fig. 3 indicates the determination of the first state Φx of the X coordinate. Furthermore, the steps can be changed within a range that does not affect the processing, or several steps can be processed in parallel at the same time.

First, the voltage generating unit 10 applies bias voltages Vb1 and Vb2 to the first terminal P1x and the second terminal P2x (S100). In this state, the voltage detecting unit 20 measures the panel voltage VPx (S102), and the current detecting unit 30 measures the panel current IPx (S104).

The arithmetic unit 40 receives the digital values VPx', IPx' corresponding to the panel voltage VPx and the panel current IPx obtained in this manner.

Then, it is determined whether the user has touch or not (S106). When the user touches the point where the X coordinate is small (near the edge E1), the panel voltage VPx rises; and when the contact with the larger point of the X coordinate (near the edge E2), the panel voltage VPx decreases. Since the voltage is not applied to the third terminal P1y in the non-contact state, the panel voltage VPx is close to 0 V.

Thereby, the coordinate generation unit 48 determines whether or not there is touch by comparing the panel voltage VPx with the specific threshold voltage Vth. The threshold voltage Vth is set to a value close to 0 V.

When VPx>Vth (Y of S106), it is determined to be in a contact state. Then, the multi-touch determination unit 42 determines whether or not multi-touch is present (S110). By comparing the panel current IPx with the specific reference current IPxo as described above, it is determined whether or not multi-touch is present.

The multi-touch determination unit 42 determines that the single touch is performed when IPx < IPxo (N of S110), and notifies the result of the determination to the coordinate generation unit 48. The coordinate generation unit 48 determines the X coordinate based on the panel voltage VPx (S118).

The multi-touch determination unit 42 determines that multi-touch is performed when IPx>IPxo (Y of S110), and notifies the distance calculation unit 44 and the coordinate generation unit 48 of the determination result.

When it is determined that the multi-touch is multi-touch, the distance calculation unit 44 determines the distance ΔX between the two points PU1 and PU2 (S112).

The inventors have recognized that there is a correlation between the distance ΔX between the two points PU1 and PU2 and the panel current IPx. That is, when the distance ΔX between two points is 0, it is the same as the single touch, and therefore the panel current IPx is substantially equal to the reference current IPxo.

4(a) and 4(b) are diagrams showing the relationship between panel current and dots in a multi-touch state.

As the distance ΔX between two points increases, the distance between the resistors R12 and R21 is increased in parallel, so that the combined impedance Zm between the first terminal P1x and the second terminal P2x is lowered, and the panel current IPx is also increased. When the distance ΔX between the two points reaches the length Lx of the panel in the X-axis direction, the panel current IPx becomes the minimum value IPxmin.

That is, the panel current IPx has a one-to-one correspondence with the distance ΔX of two points. In other words, the difference between the panel current IPx and the reference current IPxo (IPx-IPxo) has a one-to-one correspondence with the distance ΔX. Fig. 4(a) is a diagram showing the relationship between the differential current (IPx-IPxo) and the distance ΔX.

The characteristics shown in FIG. 4(a) can be measured in advance for each touch panel 4, or can be derived by simulation. Table 46 stores the relationship between the differential current (IPx-IPxo) and the distance ΔX.

The distance calculation unit 44 determines the corresponding distance ΔX based on the panel current IPx and refers to the table 46, and outputs it to the coordinate generation unit 48. Further, instead of the table 46, the approximate expression of the characteristic of FIG. 4(a) may be stored in advance, and the distance ΔX may be calculated by calculation.

The coordinate generation unit 48 receives the data indicating the distance ΔX and the panel voltage VPx3. The coordinate generation unit 48 calculates the X coordinate X3 corresponding to the panel voltage VPx3 by the same or different arithmetic method as the single touch. Then, the X coordinate X3 is taken as the center coordinate of the two points (S114).

The coordinate generation unit 48 determines the coordinate PU2 of one of the two points by adding the value (in this case, half) ΔX/2 corresponding to the coordinate interval ΔX of the two points to the center coordinate X3, and by the center coordinate X3. The value ΔX/2 corresponding to the coordinate interval ΔX of 2 points is subtracted, and the coordinate PU1 of the other of the 2 points is determined (S116). Fig. 4(b) shows the processing. Thereafter, the process returns to step S100.

Referring again to step S106, when VPx < Vth (N of S106), the coordinate generation unit 48 determines that it is in a non-contact state. Then, in step S104, the multi-touch determination unit 42 updates the reference panel current IPxo using the measured panel current IPx (S108). Thereafter, the process returns to step S100.

The above is the flow of the specific processing performed by the control circuit 100.

According to the input device 2, the single touch and the multi touch can be preferably discriminated, and the coordinates of the points in each state can be generated. Further, the input device 2 of the first embodiment has the following advantages.

In step S108, by changing the reference panel current IPxo, the influence of the deterioration of the touch panel 4 over the years, temperature fluctuations, and the like can be reduced. In other words, the values of the first resistive film RF1, the second resistive film RF2, and the contact resistances change depending on deterioration, temperature fluctuation, and the like, and accordingly, the reference current IPxo also changes. Therefore, if the reference current IPxo adopts a fixed value, erroneous detection of multi-touch may occur, or an error may occur in the distance ΔX between two points. In response to this, the problem can be better solved by updating the reference current IPxo on the way of processing.

Further, in the multi-touch state, the use of the differential current (IPx-IPxo) when determining the distance ΔX between two points has the following advantages. As described above, the impedance of the panel changes with time or temperature, so the value of the panel current IPx when the same coordinate is touched also changes. Therefore, when the differential current is calculated, the influence of deterioration over years, temperature fluctuation, and the like can be reduced, and the coordinates can be accurately detected.

Fig. 5 is a circuit diagram showing a configuration example of the current detecting unit 30 of Fig. 1. The current detecting unit 30 includes detection resistors Rsx and Rsy, bypass switches SW1x and SW1y, a selector 36, and an A/D converter 34. The detection resistors Rsx and Rsy correspond to the I/V conversion unit 32 of Fig. 1 .

The detection resistor Rsx, the bypass switch SW1x are used to detect the coordinates in the X-axis direction, and the detection resistor Rsy and the bypass switch SW1y are used to detect the coordinates in the Y-axis direction. Since the X-axis and the Y-axis are configured in the same manner, the X-axis direction will be described here.

The detection resistor Rsx is provided on an extension line including a path of the first terminal P1x, the first resistance film RF1, and the second terminal P2x. Specifically, one end of the detecting resistor Rsx is grounded and the potential is fixed, and the other end is connected to the second terminal Pc2x.

The bypass switch SW1x is provided in parallel with the corresponding detection resistor Rsx. Specifically, one end of the bypass switch SW1x is grounded, and the other end is connected to the second terminal Pc2x.

When the panel voltage VPx is detected by the voltage detecting unit 20, the bypass switch SWx is turned on. At this time, the detecting resistor Rs has no influence on the combined impedance of the touch panel 4, so the panel voltage VPx can be accurately measured.

When the panel current IPx is detected by the current detecting unit 30, the bypass switch SWx is turned off. As a result, a voltage drop (Rsx×IPx) proportional to the panel current IPx is generated at the sense resistor Rsx. The selector 36 turns on the terminal (0) side when detecting the coordinate in the X-axis direction, and turns on the terminal (1) side when detecting the coordinate in the Y-axis direction. The voltage drop of the sense resistor Rsx is converted to a digital value by the A/D converter 34. The digital value is a value corresponding to the panel current IPx.

Further, when the second bias voltage Vb2 is the ground voltage, the bypass switch SW1x can function as the voltage generating unit 10. In other words, when the second bias voltage Vb2 is applied to the second terminal P2x, the bypass switch SW1x may be turned on. The bypass switch SW1y is also the same.

(Second embodiment)

Fig. 6 is a block diagram showing the configuration of an electronic device 1 having a touch panel input device (abbreviated as input device) 2 according to the second embodiment. The input device 2 is disposed on a surface layer of, for example, an LCD (Liquid Crystal Display) 8, and functions as a touch panel. The input device 2 determines the X coordinate and the Y coordinate of a point touched by a user with a finger or a stylus pen (hereinafter referred to as finger 6).

The input device 2 includes a touch panel 4 and a control circuit 100. The touch panel 4 is a 4-wire (4-terminal) resistive film type touch panel. Since the configuration of the touch panel 4 is a common configuration, it will be briefly described herein.

The touch panel 4 includes a first terminal P1x to a fourth terminal P2y, a first resistive film RF1, and a second resistive film RF2.

The first resistive film RF1 and the second resistive film RF2 are arranged to overlap each other at intervals in the Z-axis direction perpendicular to the X-axis and the Y-axis. One side E1 of the first resistive film RF1 perpendicular to the X-axis is connected to the first terminal P1x. The side E2 opposite to the side E1 is connected to the second terminal P2x. The third terminal P1y is connected to one side E3 parallel to the X axis of the second resistive film RF2, and the fourth terminal P2y is connected to one side E4 opposite to the side E3 of the second resistive film RF2.

The above is the configuration of the touch panel 4.

The control circuit 100 determines the position of the point touched by the user while switching the first state Φx detecting the coordinate in the X direction and the second state Φy detecting the coordinate in the Y direction.

The control circuit 100 includes a first terminal Pc1x to a fourth terminal Pc2y, a voltage generating unit 10, a voltage detecting unit 20, a current detecting unit 30, and a computing unit 40.

The first terminal Pc1x to the fourth terminal Pc2y are respectively connected to the corresponding first terminal P1x to fourth terminal P2y on the touch panel 4 side.

First, the configuration for detecting the coordinate (X coordinate) in the X direction will be described.

In the first state Φx, the voltage generating unit 10 applies a specific first bias voltage Vb1 and a second bias voltage Vb2 to the first terminal P1x and the second terminal P2x, respectively. Here, Vb1>Vb2 is made. The second bias voltage Vb2 is preferably a ground voltage (0 V). Further, in the first state, the voltage generating unit 10 sets the third terminal P1y and the fourth terminal P2y to a high impedance state.

The voltage detecting unit 20 detects the panel voltage VPx generated in the third terminal P1y in the first state Φx. The voltage detecting unit 20 includes an A/D converter 24 that converts the detected panel voltage VPx into a digital signal VPx'.

The current detecting unit 30 detects the panel current IPx flowing through a path including the first terminal P1x, the first resistive film RF1, and the second terminal P2x in the first state Φx. The current detecting unit 30 includes an I/V converting unit 32 that converts the panel current IPx into a voltage signal, and an A/D converter 34 that converts the voltage signal into a digital signal VPx'.

The calculation unit (coordinate determination unit) 40 determines the X coordinate of the point PU that the user touches based on the values of the panel voltage VPx' and the panel current IPx'.

Next, the configuration for detecting the coordinate (Y coordinate) in the Y direction will be described.

In the second state Φy, the voltage generating unit 10 applies a specific first bias voltage Vb1 and a second bias voltage Vb2 to the third terminal P1y and the fourth terminal P2y, respectively. Further, in the second state, the voltage generating unit 10 sets the first terminal P1x and the second terminal P2x to a high impedance state. The first bias voltage Vb1 in each of the first state and the second state may be the same value or a different value. Hereinafter, a case where the first bias voltage Vb1 has the same value will be described. The same applies to the second bias voltage Vb2.

The voltage detecting unit 20 detects the panel voltage VPy generated in the first terminal P1x in the second state Φy. The A/D converter 24 converts the detected panel voltage VPy into a digital signal VPy'. The voltage detecting unit 20 is provided with a selector 22 having two input terminals, and the first input terminal (0) is connected to the third terminal P1y, and the second input terminal (1) is connected to the first terminal P1x. The selector 22 turns on the first input terminal (0) side in the first state Φx, and turns on the second input terminal (1) side in the second state Φx.

Further, in the first state Φx, the voltage detecting unit 20 may detect the voltage generated in the third terminal P1y or may be detected in the fourth terminal P2y in addition to the voltage generated in the third terminal P1y. The voltage is used as the panel voltage VPx. Similarly, in the second state Φy, the voltage detecting unit 20 may detect the voltage generated in the first terminal P1x or may be detected in the second terminal P2x in addition to the voltage generated in the first terminal P1x. The voltage is used as the panel voltage VPy.

The current detecting unit 30 detects a panel current IPy flowing through a path including the third terminal P1y, the second resistive film RF2, and the fourth terminal P2y in the second state Φy. The I/V conversion unit 32 converts the panel current IPy into a voltage signal, and the A/D converter 34 converts the panel current IPy into a digital value IPy'.

The calculation unit (coordinate determination unit) 40 determines the Y coordinate of the point PU that the user touches based on the values of the panel voltage VPy' and the panel current IPy'.

In other words, the third terminal P1y functions as a terminal for detecting the panel voltage VPx in the first state Φx and for applying the bias voltage Vb2 to the second resistive film RF2 in the second state Φy. Similarly, the first terminal P1x functions as a terminal for detecting the panel voltage VPy in the second state Φy and a bias voltage Vb1 for the first resistive film RF1 in the first state Φx. Further, the fourth terminal P2y may be used as a terminal for detecting the panel voltage VPx instead of the third terminal P1y, and the second terminal P1y may be used as a terminal for detecting the panel voltage VPy instead of the first terminal P1x.

The above is the overall configuration of the control circuit 100. Next, the principle of detecting the coordinates by the control circuit 100 will be described. Here, the principle of detecting the X coordinate in the first state Φx will be described, and the detection of the Y coordinate is also the same.

7(a) and 7(b) are equivalent circuit diagrams showing a single touch state and a multi-touch state, respectively. Furthermore, the respective resistors shown in the equivalent circuit are actually generated as distribution constants, and are shown as individual resistance elements for simplicity of explanation.

(single touch state)

Refer to Figure 7(a). When the user touches the PU at one point, the first resistive film RF1 is divided into a resistor R11 between the first terminal P1x and the point PU, and a resistor R12 between the point PU and the second terminal P2x. When the contact is made to the point PU, the contact resistance between the first resistive film RF1 and the second resistive film RF2 is Rc. The resistance from the point PU of the second resistive film RF2 to the path of the third terminal P1y is R2.

The potential of the point PU is obtained by dividing the bias voltages Vb1 and Vb2 by the resistors R11 and R12, and thus indicates the X coordinate of the point PU. The potential of the PU is substantially equal to the voltage of the third terminal P1y. That is, the panel voltage VPx generated in the third terminal P1y represents the X coordinate of the point PU.

The algorithm for deriving the X coordinate from the panel voltage VPx can employ a well-known technique, and is not particularly limited in the present invention.

Since the impedance on the side of the third terminal P1y observation control circuit 100 is extremely high, the panel current IPx flows through the path of the first terminal P1x, the resistors R11 and R12, and the second terminal P2x. That is, the impedance Zs between the first terminal P1x and the second terminal P2x can be given by:

Zs=R11+R12;

It is considered that Zs is a constant value irrespective of the position of the contact point PU, and is also a value which is substantially the same as the value of the impedance Zo when the user is not in contact with the user:

Zs≒Zo.

Hereinafter, the impedance of the non-contact state and the single-touch state is not particularly distinguished and is referred to as a reference impedance Zo.

In the single-touch state or the non-contact state, the panel current IPx flowing from the first terminal P1x to the second terminal P2x can be given by:

IPxo=(Vb1-Vb2)/Zo.

This panel current IPxo is referred to as a reference panel current.

(multi-touch state)

Refer to Figure 7(b). When the user touches the two points PU1 and PU2, the first resistive film RF1 is divided into the resistor R11 between the first terminal P1x and the point PU1, the resistor R12 between the point PU1 and the point PU2, and the point PU2 and the second terminal. Resistance R13 between P2x. When contacting the points PU1 and PU2, the contact resistances of the first resistive film RF1 and the second resistive film RF2 are Rc1 and Rc2, respectively.

In the second resistive film RF2, the resistance between the points PU1 and PU2 is R21, the resistance of the path from the point PU1 to the third terminal P1y is R22, and the resistance of the path from the point PU2 to the third terminal P1y is R23.

The panel current IPx in the multi-touch state depends on the combined impedance Zm between the first terminal P1x and the second terminal P2x. The resultant impedance Zm has the following relationship with the impedance Zo of the non-contact state or the single-touch state:

Zm<Zo.

Therefore, the following relationship exists between the panel current IPxm in the multi-touch state and the reference panel current IPxo:

IPxm>IPxo.

That is, by monitoring the panel current IPx and comparing it with the reference panel current IPxo, the multi-touch state and the single-touch state (non-contact state) can be distinguished.

The potentials of the points PU1 and PU2 are obtained by dividing the bias voltages Vb1 and Vb2 by the resistors R11, R12, and R13 and other resistance components, and are associated with the respective X coordinates of the points PU1 and PU2. Further, the panel voltage VPx generated in the third terminal P1y is also associated with the two points PU1 and PU2. Therefore, if the multi-touch state is known, the coordinates of the points PU1 and PU2 can be estimated from the panel voltage VPx.

Further, one X coordinate X3 determined according to the panel voltage VPx and the same algorithm as the single touch state indicates the coordinates of any point between the points PU1 and PU2 that the user touches. That is, when the true X coordinates X1 and X2 of the points PU1 and PU2 are written, the following relationship exists:

X1 < X3 < X2.

That is, if the coordinates X3 derived from the panel voltage VPx are used, the coordinates of the points PU1 and PU2 can be estimated. As for the inference algorithm, it will be explained below.

As described above, according to the control circuit 100 of the second embodiment, the panel current IPx is monitored in addition to the monitor panel voltage VPx, and the combination processing is performed to determine not only the single touch state but also the multi-touch control. The coordinates of the user contact point in the state.

Next, a specific configuration example and processing of the arithmetic unit 40 will be described.

The calculation unit 40 includes a multi-touch determination unit 42, a distance calculation unit 44, a table 46, and a coordinate generation unit 48.

Figure 8 is a flow chart showing the processing in the control circuit of Figure 6. The flow of Fig. 8 indicates the determination of the first state Φx of the X coordinate. Furthermore, the steps can be changed within a range that does not affect the processing, and several steps can be processed in parallel at the same time.

First, the voltage generating unit 10 applies bias voltages Vb1 and Vb2 to the first terminal P1x and the second terminal P2x (S100). In this state, the voltage detecting unit 20 measures the panel voltage VPx (S102), and the current detecting unit 30 measures the panel current IPx (S104).

The arithmetic unit 40 receives the digit values VPx', IPx' corresponding to the panel voltage VPx and the panel current IPx obtained in this manner.

Then, it is determined whether the user has touch or not (S106). The panel voltage VPx rises when the user touches the point where the X coordinate is smaller (near the side E1), and the panel voltage VPx decreases when it contacts the point where the X coordinate is larger (near the side E2). In the non-contact state, no voltage is applied to the third terminal P1y, so the panel voltage VPx is close to 0 V.

Thereby, the coordinate generation unit 48 determines whether or not there is touch by comparing the panel voltage VPx with the specific threshold voltage Vth. The threshold voltage Vth is set to a value close to 0 V.

When VPx>Vth (Y of S106), it is determined to be in a contact state. Then, the multi-touch determination unit 42 determines whether or not multi-touch is present (S110). By comparing the panel current IPx with the specific reference current IPxo as described above, it is determined whether or not multi-touch is present.

The multi-touch determination unit 42 determines that the single touch is performed when IPx < IPxo (N of S110), and notifies the result of the determination to the coordinate generation unit 48. The coordinate generation unit 48 determines the X coordinate based on the panel voltage VPx (S118).

The multi-touch determination unit 42 determines that multi-touch is performed when IPx>IPxo (Y of S110), and notifies the distance calculation unit 44 and the coordinate generation unit 48 of the determination result.

When it is determined that the multi-touch is multi-touch, the distance calculation unit 44 determines the distance ΔX between the two points PU1 and PU2 (S112).

The inventors have recognized that there is a correlation between the distance ΔX between the two points PU1 and PU2 and the panel current IPx. That is, when the distance ΔX between two points is 0, it is the same as the single touch, and therefore the panel current IPx is substantially equal to the reference current IPxo.

9(a) and 9(b) are diagrams showing the relationship between panel current and dots in a multi-touch state.

As the distance ΔX between two points increases, the distance between the resistors R12 and R21 is increased in parallel, so that the combined impedance Zm between the first terminal P1x and the second terminal P2x is lowered, and the panel current IPx is also increased. When the distance ΔX between the two points reaches the length Lx of the panel in the X-axis direction, the panel current IPx becomes the minimum value IPxmin.

That is, the panel current IPx has a one-to-one correspondence with the distance ΔX of two points. In other words, the difference (IPx-IPxo) between the panel current IPx and the reference current IPxo is in one-to-one correspondence with the distance ΔX. Fig. 9(a) is a diagram showing the relationship between the differential current (IPx-IPxo) and the distance ΔX.

The characteristics shown in FIG. 9(a) can be measured in advance for each touch panel 4, and can also be derived by simulation. Table 46 stores the relationship between the differential current (IPx-IPxo) and the distance ΔX.

The distance calculation unit 44 determines the corresponding distance ΔX based on the panel current IPx and refers to the table 46, and outputs it to the coordinate generation unit 48. Further, instead of the table 46, the approximate expression of the characteristic of Fig. 9(a) may be stored in advance, and the distance ΔX is calculated by the operation.

The coordinate generation unit 48 receives the data indicating the distance ΔX and the panel voltage VPx. The coordinate generation unit 48 calculates the X coordinate X3 corresponding to the panel voltage VPx by the same or different arithmetic method as the single touch. Then, the X coordinate X3 is set to the center coordinate of 2 points (S114).

The coordinate generation unit 48 determines the coordinate PU2 of one of the two points by adding the value (here, half) ΔX/2 corresponding to the coordinate interval ΔX of the two points to the central coordinate X3, and subtracts it from the central coordinate X3. The coordinate PU1 of the other of the two points is determined by the value ΔX/2 corresponding to the coordinate interval ΔX of the two points (S116). Fig. 9(b) shows the processing. Thereafter, the process returns to step S100.

Referring again to step S106, when VPx < Vth (N of S106), the coordinate generation unit 48 determines that it is in a non-contact state. Then, in step S104, the multi-touch determination unit 42 updates the reference panel current IPxo using the measured panel current IPx (S108). Thereafter, the process returns to step S100.

The above is the flow of the specific processing performed by the control circuit 100.

According to the input device 2, the single touch and the multi touch can be preferably discriminated, and the coordinates of the points in each state can be generated. Further, the input device 2 of the second embodiment has the following advantages.

In step S108, the influence of the deterioration of the touch panel 4 over the years, the temperature fluctuation, and the like can be reduced by updating the reference panel current IPxo. In other words, when the values of the first resistive film RF1, the second resistive film RF2, and the contact resistances change in accordance with deterioration, temperature fluctuation, or the like, the reference current IPxo also changes. Therefore, if the reference current IPxo adopts a fixed value, it will lead to erroneous detection of multi-touch, or an error in the distance ΔX between two points. In response to this, the problem can be better solved by updating the reference current IPxo on the way of processing.

Further, in the multi-touch state, the use of the differential current (IPx-IPxo) in determining the distance ΔX between two points has the following advantages. As described above, since the impedance of the panel changes with time or temperature, the value of the panel current IPx when the same coordinate is touched also changes. Therefore, when the differential current is calculated, the influence of deterioration over years, temperature fluctuation, and the like can be reduced, and the coordinates can be accurately detected.

Fig. 10 is a circuit diagram showing a configuration example of the current detecting unit of Fig. 6. The current detecting unit 30 includes detection resistors Rsx and Rsy, bypass switches SW1x and SW1y, a selector 36, and an A/D converter 34. The detection resistors Rsx and Rsy correspond to the I/V conversion unit 32 of Fig. 6 .

The detection resistor Rsx, the bypass switch SW1x are used to detect the coordinates in the X-axis direction, and the detection resistor Rsy and the bypass switch SW1y are used to detect the coordinates in the Y-axis direction. Since the X axis and the Y axis are configured in the same manner, only the X axis direction will be described here.

The detection resistor Rsx is provided on an extension line including a path of the first terminal P1x, the first resistance film RF1, and the second terminal P2x. Specifically, one end of the detecting resistor Rsx is grounded and the potential is fixed, and the other end is connected to the second terminal Pc2x.

The bypass switch SW1x is provided in parallel with the corresponding detection resistor Rsx. Specifically, one end of the bypass switch SW1x is grounded, and the other end is connected to the second terminal Pc2x.

When the panel voltage VPx is detected by the voltage detecting unit 20, the bypass switch SWx is turned on. At this time, the detecting resistor Rs does not affect the combined impedance of the touch panel 4, so the panel voltage VPx can be accurately measured.

When the panel current IPx is detected by the current detecting unit 30, the bypass switch SWx is turned off. As a result, a voltage drop (Rsx×IPx) proportional to the panel current IPx is generated at the sense resistor Rsx. When the selector 36 detects the coordinates in the X-axis direction, the terminal (0) side is turned on, and when the coordinate in the Y-axis direction is detected, the terminal (1) side is turned on. The voltage drop of the sense resistor Rsx is converted to a digital value by the A/D converter 34. The digital value is a value corresponding to the panel current IPx.

Further, when the second bias voltage Vb2 is the ground voltage, the bypass switch SW1x can be made to function as the voltage generating unit 10. In other words, when the second bias voltage Vb2 is applied to the second terminal P2x, the bypass switch SW1x may be turned on. The bypass switch SW1y is also the same.

Fig. 11 is a circuit diagram showing another configuration example of a part of the control circuit of Fig. 6.

The voltage generating unit 10a of the control circuit 100a includes a regulator 11, a first selector SEL1, and a second selector SEL2.

The regulator 11 and the first selector SEL1 generate the first bias voltage Vb1, apply the first bias voltage Vb1 to the first terminal P1x in the first state Φx, and apply the third terminal P1y to the second terminal Φy in the second state Φy. The first bias voltage Vb1.

The regulator 11 generates a first bias voltage Vb1 corresponding to the reference voltage Vref. Since the regulator 11 is a general linear regulator including the operational amplifier 12, the output transistor 14, the first resistor R1, and the second resistor R2, the description of the configuration and operation will be omitted. The first bias voltage Vb1 can be given by:

Vb1 = Vref × (R1 + R2) / R2.

The value of the reference voltage Vref may be switched in the first state Φx and the second state Φy.

The first selector SEL1 receives the first bias voltage Vb1 at the input terminal. The first selector SEL1 has a first terminal Pc1x connected to the first output terminal (0), and a third terminal Pc1y is connected to the second output terminal (1). The first selector SEL1 turns on the first output terminal (0) side in the first state Φx, and turns on the second output terminal (1) side in the second state Φy. For example, the first selector SEL1 includes switches SWa1 and SWa2 that are turned on and off complementarily.

The second selector SEL2 is provided to apply the second bias voltage Vb2 to the touch panel 4. The second bias voltage Vb2 is a ground voltage, and the second selector SEL2 includes switches SWb1 and SWb2 that are turned on and off complementarily. In the first state Φx, the switch SWb1 is turned on, and in the second state Φy, the switch SWb2 is turned on.

The current detecting unit 30a includes a detecting transistor 38, a detecting resistor Rs, and an A/D converter 34. The detection transistor 38 is connected to the output transistor 14 of the regulator 11 in the form of a current mirror. A detection current Is which is proportional to the current flowing through the output transistor 14, that is, the panel current, flows through the detection transistor 38. When the mirror ratio of the current mirror circuit is recorded as K1, the following relationship exists:

Is=K1×IP.

The detecting resistor Rs is disposed on the path of the detecting transistor 38. A voltage drop Vs proportional to the sense current Is is generated in the sense resistor Rs, and the voltage drop Vs is proportional to the panel current IP:

Vs = Rs × Is = Rs × K1 × IP.

The A/D converter 34 converts the voltage drop Vs generated in the detecting resistor Rs into a digital value and outputs it as signals IPx', IPy' indicating the panel current IP.

The control circuit 100a of Fig. 11 has the following advantages as compared with the control circuit of the current detecting unit 30 of Fig. 10.

In the control circuit 100a of FIG. 11, the detecting resistor Rs for converting the panel current IP into a voltage is not directly connected to the touch panel 4. Therefore, the panel current IP can be detected without affecting the panel voltage VP.

On the other hand, in the case of using the current detecting unit 30 of FIG. 10, it is necessary to switch the bypass switch SW1x (or SW1y) to measure the state of the panel voltage VPx (or VPy), and to bypass the switch SW1x (or SW1y) is disconnected to determine the state of the panel current IPx (or IPy), so that it is time consuming to detect the coordinates. Further, since the panel voltage VPx and the panel current IPx (or VPy and IPy) are measured at different timings, the measurement accuracy of the coordinates is inferior.

In view of this, the control circuit 100a of FIG. 11 can simultaneously measure the panel voltage and the panel current in parallel, so that the processing can be speeded up, and is suitable for an application requiring high speed. Since the two parameters, voltage and current, which are necessary for determining the coordinates, can be obtained at the same time, the coordinates can be accurately determined.

Further, the difference ΔI between the panel current at the time of one-point contact and the panel current at the time of the two-point contact is extremely small due to the panel. In this case, in the control circuit 100 of FIG. 10, the voltage drop change ΔV generated in the sense resistor Rs is, for example, a current difference of ΔI=200 μA, and when the sense resistor Rs is 200 Ω, it is only ΔV=40 mV. This means that the A/D converter 34 is required to have high resolution performance, which is difficult to design or leads to an increase in cost.

In view of this, in the control circuit 100a of FIG. 11, the variation ΔV of the voltage drop Vs of the detecting resistor Rs can be sufficiently ensured by optimizing the mirror ratio K1, so that the accuracy required for the A/D converter 34 can be reduced.

The current detecting unit 30a can also switch the mirror ratio K1 of the output transistor 14 and the detecting transistor 38 in the first state Φx and the second state Φy. The detection resistor Rs may be set as a variable resistor instead of the mirror ratio switching, or the current detecting unit 30a may switch the resistance value of the detecting resistor Rs in the first state Φx and the second state Φy in addition to the mirror ratio switching.

When the longitudinal length and the lateral length (ie, the aspect ratio) of the touch panel 4 are largely different, the longitudinal composite resistance is different from the lateral composite resistance, and the panel current IPx range and the Y direction panel current in the X direction are different. The range of IPy is different. In this case, by switching the values of the mirror ratio K1 or the sense resistor Rs in the first state Φx and the second state Φy, the voltage range of the voltage drop Vs of the sense resistor Rs can be made uniform, and the shared A/ can be shared. The D converter 34 performs processing with high precision.

The output transistor 14 and the detecting transistor 38 of FIG. 11 form a current mirror circuit, which can also be used as a stacked current mirror circuit. In this case, the accuracy of the replica current can be improved, that is, the accuracy of the mirror ratio can be improved.

Fig. 12 is a circuit diagram showing a modification of the control circuit of Fig. 6. In the control circuit 100b of Fig. 12, the processing of the panel voltage VP is different from the processing of the panel voltage VP of Fig. 6. In other words, the voltage detecting unit 20 of FIG. 6 detects the panel voltage VPx generated in the third terminal P1y in the first state Φx, and detects the panel voltage VPy generated in the first terminal P1x in the second state Φy. On the other hand, in the first state Φx, the voltage detecting unit 20b of FIG. 12 individually detects the panel voltages VPx_1 and VPx_2 generated in the third terminal P1y and the fourth terminal P2y, and in the second state Φ2, individually. The panel voltages VPy_1 and VPy_2 generated in the first terminal P1x and the second terminal P2x, respectively, are detected.

The voltage detecting unit 20b includes switches SW4 to SW7 and an A/D converter 24. The switches SW4 to SW7 correspond to the selector 22 of FIG.

In the first state Φx, the switch SW4 is first turned on, and the remaining switches are turned off. The panel voltage VPx_1 of the third terminal P1y is measured in this state. Then, the switch SW5 is turned on, and the remaining switches are turned off. The panel voltage VPx_2 of the fourth terminal P2y is measured in this state. The calculation unit 40 (not shown) of the subsequent stage determines the X coordinate of the point PU that the user touches based on the values of the two panel voltages VPx_1, VPx_2 and the panel current IPx.

Similarly, in the second state Φy, the switch SW6 is first turned on, and the remaining switches are turned off. The panel voltage VPy_1 of the first terminal P1x is measured in this state. Then, the switch SW7 is turned on, and the remaining switches are turned off. The panel voltage VPy_2 of the second terminal P2x is measured in this state. The calculation unit 40 (not shown) of the subsequent stage determines the Y coordinate of the point PU that the user touches based on the values of the two panel voltages VPy_1 and VPy_2 and the panel current IPy.

According to this modification, the panel voltage of the two terminals can be measured in the first state Φx and the second state Φy, respectively, and reflected in the determination of the X coordinate and the Y coordinate, whereby the accuracy of the detection coordinate can be improved.

Further, the features of the modification of Fig. 12 can also be combined with the control circuit of Fig. 11.

The present invention has been described above based on the first and second embodiments. It will be apparent to those skilled in the art that these embodiments are merely illustrative, and that various modifications may be obtained in combination of the various components or processes, and such modifications are also within the scope of the invention. Hereinafter, such a modification will be described.

In the multi-touch state, the coordinate generation unit 48 estimates that the coordinate X3 corresponding to the panel voltage VPx is a point between the two points PU1 and PU2, and determines the original coordinates X1 and X2. However, the present invention is not limited thereto, and a more complicated algorithm can be employed.

In the embodiment, the first state Φx and the second state Φy are configured to share one of the control circuits 100 of FIG. 1, but they may be completely provided separately. Alternatively, the present invention can be applied to only one of the X direction and the Y direction.

In the embodiment, the case of controlling the touch panel 4 of the four terminals has been described. However, the present invention is not limited thereto, and can be applied to other touch panels 4.

Further, in the embodiment, multi-touch is described by taking two points as an example. However, those skilled in the art can expand it to more than 3 points, which is also included in the present invention.

The present invention has been described based on the embodiments and using specific statements. However, the embodiments are merely illustrative of the principles and applications of the present invention, and various modifications and changes can be made in the embodiments without departing from the scope of the invention as defined by the appended claims.

1. . . Electronic machine

2. . . Input device

4. . . Touch panel

6. . . finger

8. . . LCD

10, 10a. . . Voltage generation unit

11. . . Regulator

12. . . Operational Amplifier

14. . . Output transistor

20, 20b. . . Voltage detection unit

22, 36, SEL1, SEL2. . . Selector

24, 34. . . A/D converter

30, 30a. . . Current detection unit

32. . . I/V conversion department

38. . . Detecting transistor

40. . . Computing department

42. . . Multi-touch determination unit

44. . . Distance calculation department

46. . . form

48. . . Coordinate generation unit

100, 100a, 100b. . . Control circuit

E1, E2. . . Side of RF1

E3, E4. . . Edge of RF2

IP, IPx, IPx', IPxo, IPy, IPy'. . . Panel current

Lx. . . The length of the panel in the X direction

P1x, Pc1x. . . First terminal

P2x, Pc2x. . . Second terminal

P1y, Pc1y. . . Third terminal

P2y, Pc2y. . . Terminal 4

PU, PU1, PU2. . . User touch point

R1, R2, R11, R12, R13, R21, R22, R23. . . resistance

Rc, Rc1, Rc2. . . Contact resistance

RF1, RF2. . . Resistive film

Rsx, Rsy. . . Sense resistor

SW1x, SW1y, SW4~SW7, SWa1, SWa2, SWb1, SWb2. . . switch

Vb1, Vb2. . . Bias voltage

VPx, VPx', VPy, VPy'. . . Panel voltage

X3. . . Center coordinates

ΔX, ΔY. . . Point PU1, PU2 distance

Φx. . . First state

Φy. . . Second state

1 is a block diagram showing the configuration of an electronic device having the touch panel input device of the first embodiment;

2(a) and (b) are equivalent circuit diagrams showing a single touch state and a multi-touch state, respectively;

Figure 3 is a flow chart showing the processing in the control circuit of Figure 1;

4(a) and 4(b) are diagrams showing the relationship between panel current and dots in a multi-touch state;

Fig. 5 is a circuit diagram showing a configuration example of the current detecting unit of Fig. 1;

6 is a block diagram showing the configuration of an electronic device having the touch panel input device of the second embodiment;

7(a) and 7(b) are respectively equivalent circuit diagrams showing a single touch state and a multi-touch state;

Figure 8 is a flow chart showing the processing in the control circuit of Figure 6;

9(a) and 9(b) are diagrams showing the relationship between panel current and dots in a multi-touch state;

Fig. 10 is a circuit diagram showing a configuration example of the current detecting unit of Fig. 6;

Figure 11 is a circuit diagram showing another configuration example of the control circuit of Figure 6;

Fig. 12 is a circuit diagram showing still another example of the configuration of the control circuit of Fig. 6.

1. . . Electronic machine

2. . . Input device

4. . . Touch panel

6. . . finger

8. . . LCD

10. . . Voltage generation unit

20. . . Voltage detection unit

twenty two. . . Selector

24, 34. . . A/D converter

30. . . Current detection unit

32. . . I/V conversion department

40. . . Computing department

42. . . Multi-touch determination unit

44. . . Distance calculation department

46. . . form

48. . . Coordinate generation unit

100. . . Control circuit

E1, E2. . . Side of RF1

E3, E4. . . Edge of RF2

IPx, IPy, IPx', IPy'. . . Panel current

P1x, Pc1x. . . First terminal

P2x, Pc2x. . . Second terminal

P1y, Pc1y. . . Third terminal

P2y, Pc2y. . . Terminal 4

PU. . . User touch point

RF1, RF2. . . Resistive film

Vb1, Vb2. . . Bias voltage

VPx, VPx', VPy, VPy'. . . Panel voltage

ΔX, ΔY. . . Point PU1, PU2 distance

Φx. . . First state

Φy. . . Second state

Claims (26)

A control method for a touch panel, the touch panel includes: first, second, and third terminals; and a first resistive film connected to the first terminal and opposite to the side And being connected to the second terminal; and the second resistive film is disposed in a gap from the first resistive film and connected to the third terminal; and includes the step of: the first and second terminals Applying a specific first and second bias voltages respectively; detecting a panel voltage generated in the third terminal; and detecting a panel current flowing through a path including the first terminal, the first resistive film, and the second terminal; And determining a coordinate touched by the user according to the panel voltage and the panel current. The control method of the touch panel of claim 1, wherein when the value of the panel current is greater than a specific value, it is determined that the user contacts a plurality of points. The control method of the touch panel of claim 1, wherein when the user contacts the two points, the coordinate interval of the two points is determined according to the value of the panel current. The control method of the touch panel of claim 3, wherein the larger the panel current is, the larger the coordinate interval of the two points is determined. The control method of the touch panel of claim 3, wherein the coordinate interval of the two points is determined according to a difference between the panel current measured when the user does not touch the panel and the panel current when the user touches. The control method of the touch panel of claim 3, wherein the determining step The method includes the steps of: determining a center coordinate of the two points according to the panel voltage; and adding a value corresponding to the coordinate of the two points to the center coordinate, thereby determining one of the two points and from the center The coordinate is subtracted from the value corresponding to the coordinate interval of the above two points, thereby determining the coordinates of the other of the above two points. A control circuit is characterized in that it is a control circuit of a touch panel, the touch panel includes: first, second, and third terminals; and a first resistive film, one side of which is connected to the first terminal, and The side opposite to the second terminal is connected to the second terminal; and the second resistive film is disposed apart from the first resistive film and is connected to the third terminal; and includes a voltage generating portion. a specific first and second bias voltages are applied to the first and second terminals, a voltage detecting unit detects a panel voltage generated in the third terminal, and a current detecting unit that detects the flow includes the first a panel current of a path of the terminal, the first resistive film and the second terminal; and a coordinate determining unit that determines a coordinate to be contacted by the user based on the panel voltage and the value of the panel current. The control circuit of claim 7, wherein the coordinate determining unit determines that the user contacts the plurality of points when the value of the panel current is greater than a specific value. The control circuit of claim 7, wherein when the user contacts the two points, the coordinate interval of the two points is determined according to the value of the panel current. The control circuit of claim 9, wherein the coordinate interval of the two points is determined according to a difference between the panel current measured when the user does not touch the panel and the panel current when contacting the panel. The control circuit of claim 9, wherein the coordinate determining unit determines a center coordinate of two points based on the panel voltage, and adds a value corresponding to a coordinate interval of the two points to the center coordinate, thereby determining the two points. One of the coordinates of the other side, and the value corresponding to the coordinate interval of the two points is subtracted from the central coordinate to determine the coordinates of the other of the two points. The control circuit according to any one of claims 7 to 11, wherein the current detecting unit includes: a detecting resistor provided on an extension line of a path including the first terminal, the first resistive film, and the second terminal; And a bypass switch that is provided in parallel with the detection resistor; and when the panel voltage is detected by the voltage detecting unit, the bypass switch is turned on; and when the panel current is detected by the current detecting unit, The bypass switch is turned off, and a value corresponding to the voltage drop of the detecting resistor is output as a value indicating the panel current. A touch panel input device includes: a touch panel including: first, second, and third terminals; and a first resistive film connected to the first terminal and opposite to the side a second terminal connected to the second terminal; and a second resistive film which is disposed to be spaced apart from the first resistive film and connected to the third terminal; and any one of claims 7 to 11 a control circuit that controls the above touch Control panel. An electronic device operable by contact, characterized by comprising a touch panel input device as claimed in claim 13. A control circuit is characterized in that it is a control circuit of a touch panel, the touch panel includes: first, second, and third terminals; and a first resistive film, one side of which is connected to the first terminal, and The side opposite to the second terminal is connected to the second terminal; and the second resistive film is disposed apart from the first resistive film and is connected to the third terminal; and includes a voltage generating unit. The first and second bias voltages are respectively applied to the first and second terminals, the voltage detecting unit detects a panel voltage generated in the third terminal, and the current detecting unit detects that the flow includes the first a panel current of a path of the one terminal, the first resistive film and the second terminal; and a coordinate determining unit that determines a coordinate that the user touches based on the panel voltage and the value of the panel current; and the voltage generating unit includes: An output transistor that is disposed on an extension line of the first terminal side including a path of the first terminal, the first resistance film, and the second terminal, and a regulator that applies the first bias to the first terminal Voltage The current detecting unit comprises: a detection transistor which forms a current mirror output electrically connected to said crystal And a detecting resistor disposed on the path of the detecting transistor; and outputting a value corresponding to the voltage drop of the detecting resistor as a value indicating the panel current. A control circuit is characterized in that it is a control circuit for a touch panel, the touch panel includes: first, second, third, and fourth terminals; and a first resistive film, one side of which is connected to the first terminal, And connecting the second terminal to the side opposite to the side; and the second resistive film is disposed in a gap from the first resistive film, and is connected to the third terminal and is connected to the side The opposite side is connected to the fourth terminal; and includes a voltage generating unit that applies a specific first and second bias voltages to the first and second terminals in the first state, and causes the first 3. The fourth terminal is in a high impedance state; in the second state, the first and second bias voltages are respectively applied to the third and fourth terminals, and the first and second terminals are in a high impedance state; The voltage detecting unit detects a panel voltage generated in one of the third and fourth terminals in the first state, and detects a panel voltage generated in one of the first and second terminals in the second state. a current detecting unit that detects that the first terminal is included in the first state, a panel current of a path between the first resistive film and the second terminal; and a panel current flowing through a path including the third terminal, the second resistive film, and the fourth terminal in the second state; and a coordinate determination a portion that determines a coordinate that the user touches based on the panel voltage and the value of the panel current; and The voltage generating unit includes: a regulator having an output transistor and generating the first bias voltage; and a selector that receives the first bias voltage at an input terminal and connects the first output terminal to the first output terminal The terminal is connected to the third terminal, and the third terminal is connected to the first output terminal side in the first state, and the second output terminal side is turned on in the second state. The current detecting unit includes a detecting transistor connected to the output transistor in a current mirror form; and a detecting resistor disposed on a path of the detecting transistor; and a value corresponding to a voltage drop of the detecting resistor is used to represent the panel current The value is output. A control circuit is characterized in that it is a control circuit for a touch panel, and the touch panel includes: first, second, third, and fourth terminals: a first resistive film, one side of which is connected to the first terminal, And connecting the second terminal to the side opposite to the side; and the second resistive film is disposed in a gap from the first resistive film, and is connected to the third terminal and is connected to the side The opposite side is connected to the fourth terminal; and includes a voltage generating unit that applies a specific first and second bias voltages to the first and second terminals in the first state, and causes the first 3. The fourth terminal is in a high impedance state; in the second state, the first and second bias voltages are respectively applied to the third and fourth terminals, and the first and second terminals are in a high impedance state; The voltage detecting unit individually detects the panel voltages generated in the third and fourth terminals in the first state, and individually detects the respective first and second terminals in the second state. a panel voltage; a current detecting unit that detects a panel current flowing through a path including the first terminal, the first resistive film, and the second terminal in the first state, and detects that the flow in the second state includes the above a panel current of a path of the third terminal, the second resistive film, and the fourth terminal; and a coordinate determining unit that determines a coordinate that the user touches based on the panel voltage and the value of the panel current; and the voltage generating unit includes a regulator having an output transistor and generating the first bias voltage; and a selector for receiving the first bias voltage at an input terminal and connecting the first terminal to the first output terminal, The output terminal is connected to the third terminal, and the first output terminal side is turned on in the first state, and the second output terminal side is turned on in the second state. The current detecting unit includes a detecting transistor connected to the output transistor in a current mirror form; and a detecting resistor disposed on a path of the detecting transistor; and a value corresponding to a voltage drop of the detecting resistor is used to represent the panel current The value is output. The control circuit of claim 16 or 17, wherein the current detecting unit is configured The mirror ratio of the output transistor to the detection transistor can be switched between the first state and the second state. The control circuit according to claim 16 or 17, wherein the current detecting unit is configured to switch the resistance value of the detecting resistor in the first state and the second state. The control circuit according to any one of claims 15 to 17, wherein the coordinate determining unit determines that the user contacts the plurality of points when the value of the panel current is greater than a specific value. The control circuit according to any one of claims 15 to 17, wherein when the user touches 2 points, the coordinate interval of the 2 points is determined according to the value of the panel current. The control circuit of claim 21 determines the coordinate interval of the two points according to the difference between the panel current measured when the user does not touch the panel and the panel current when the user touches. The control circuit of claim 21, wherein the coordinate determining unit determines the center coordinates of the two points based on the panel voltage, and adds the value corresponding to the coordinates of the coordinates of the two points to determine the two points. The coordinate of one of the two points is determined by subtracting the value corresponding to the coordinate interval of the above two points from the central coordinate to determine the coordinates of the other of the two points. A touch panel input device includes: a touch panel including: first, second, and third terminals; and a first resistive film connected to the first terminal and opposite to the side a second terminal connected to the second terminal; and a second resistive film connected to the first electric The resistive film is disposed with a gap therebetween, and is connected to the third terminal; and a control circuit according to any one of claims 15 to 17, which controls the touch panel. An electronic device operable by contact, comprising a touch panel input device as claimed in claim 24. A control method for a touch panel, the touch panel includes: first, second, and third terminals; and a first resistive film connected to the first terminal and opposite to the side And being connected to the second terminal; and the second resistive film is disposed to be spaced apart from the first resistive film and connected to the third terminal; and includes the step of: And applying a specific first and second bias voltages to the second terminal, wherein the regulator includes the first terminal side disposed on a path including the first terminal, the first resistive film, and the second terminal. Extending an output transistor on the line, applying the first bias voltage to the first terminal, detecting a panel voltage generated in the third terminal, and detecting a transistor connected to the output transistor by a current mirror; a detection resistor provided on a path of the detection transistor detects a value corresponding to a voltage drop of the detection resistor as a panel indicating a path through the first terminal, the first resistance film, and the second terminal Current Value; and determining the coordinates of the user according to the contact value of the panel voltage and current of the panel.